ASoC: wm_adsp: Add debug audio trace firmware

The audio trace firmware allows the capture of arbitrary streams of
audio from the DSP and commonly used for debugging other firmwares. This
patch adds support for this firwmare into the ADSP driver.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>